Abstract
In this paper, we will present a study on magnetic viscosity of alumite perpendicular media at different thicknesses. Viscosity as a function of applied field(viscosity curve) exhibits a short plateau at low field and then decreases monotonously with increasing field. After correcting for the demagnetizing field, the shape of the intrinsic viscosity curves changes to the well-known shape of viscosity curve of in-plane media, i.e. they have a peak near H_c. The intrinsic viscosity curves obtained from experiments were fitted to an analytical model of Chantrell et al. [1], from which , we found that the effective switching volumes obtained by fitting are much smaller than the column volumes, indicating that the reversal mechanism is incoherent.
